Functional changes, following X-irradiation of the right visual with 3,500 rads in a single exposure, are monitored by evoked electroencephalographic responses of the right and the left homologous, non-irradiated cortex, from photic stimulation of the retina. Cerebral spinal fluid pressure, in the spinal subarachnoid space, is monitored by a catheter-reservoir system. Funduscopic changes are recorded by an appropriate camera. Structural changes are recorded by an appropriate camera. Structural changes are determined at sequential intervals by examination with routine and special histological techniques. With the preceding, two phenomena are receiving especial attention: Delayed brain swelling and retrograde transsynaptic degeneration in the visual system.